The determination of technetium-99 in the brown marine alga Fucus Spiralis collected along the Belgian coast

The brown alga Fucus spiralis (Fucales) grows along the Belgian coast in sufficient amount to permit regular sampling. The algae were collected at four different places (Nieuwpoort, Oostende, Blankenberge and Zeebrugge) from March 1985 to February 1986. The method used to determine ⁹⁹Tc and the subsequent results are reported. The concentration of ⁹⁹Tc (Bq kg^-1 dry weight) in whole plants was found to increase as a function of time. In addition, analyses on separated parts have revealed that, generally, apical fragments possess a lower content of ⁹⁹Tc than the middle and basal ones. These results suggest that the old tissues of Fucus spiralis, present in middle and basal fragments, have integrated technetium uptake over a period of few years, in contrast to the young ones of the apices, which have probably fixed this radionuclide only during a short period of time. The concentration factors (CFs), evaluated on the basis of 3 mBq ⁹⁹Tc ℓ^-1 seawater, varied from 8,000 to 36,000 in whole plants, reaching however 51,000 in middle fragments. These figures are of the same order of magnitude than those reported for related species of Fucus collected along the French coast of the Channel. It adds further evidence that Fucus spiralis may be used as a bioindicator for ⁹⁹Tc contamination of coastal waters.